Mounting structure of electronic component

ABSTRACT

A mounting structure of an electronic component includes: a bump electrode included in the electronic component, the bump electrode having an internal resin as a core and a conductive film covering a surface of the internal resin, and elastically deforming so as to follow a shape of at least one corner of a terminal so that the conductive film makes direct conductive contact with at least part of a top surface of the terminal and at least part of a surface along a thickness direction of the terminal; a substrate having the terminal and the electronic component that is mounted on the substrate; and a holding unit provided to the substrate and the electronic component so as to hold a state in which the bump electrode electrically deformed makes conductive contact with the terminal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. application Ser. No.12/178,055 filed Jul. 23, 2008, which claims priority to Japanese PatentApplication No. 2007-214512, filed Aug. 21, 2007 which is expresslyincorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to a mounting structure of an electroniccomponent.

2. Related Art

Mounting techniques are used in mounting, on a substrate, electroniccomponents such as semiconductor integrated circuit, in order tomanufacture a circuit substrate mounted on various electronicapparatuses as well as liquid crystal devices. A liquid crystal displaydevice, for instance, includes an integrated circuit (IC) chip forliquid crystal drive so as to drive the liquid crystal panel mountedthereon. This IC chip for liquid crystal drive may also be mounteddirectly on a glass substrate that constitutes the liquid crystal panel,or, may be mounted on a flexible substrate (FPC) which is mounted on theliquid crystal panel. A mounting structure mounted by the formertechnique is called a chip on glass (COG) structure, and a mountingstructure mounted by the latter is called a chip on flexible printcircuit (COF) structure. In addition to these mounting structures, achip on board (COB) structure may also be used. In this structure, an ICchip is mounted on, for instance, a glass-epoxy substrate.

Substrates used for such mounting structures include lands (terminals)coupled to a wiring pattern, and electronic components used include bumpelectrodes for obtaining electric connection. Mounting structures ofelectronic components are formed by mounting electronic components onthe substrates in a state in which the lands are coupled to the bumpelectrodes.

It has been desired that, in those mounting structures, electroniccomponents be firmly and securely coupled to substrates. Particularly,in the case where there are pluralities of lands and bump electrodes,and where the lands are coupled to the bump electrodes, it is importantthat all the lands and bumps are coupled well, in order to ensurereliability.

However, since lands and bump electrodes are generally formed withmetal, a mispositioning during bonding and a misalignment caused by alow aligning precision of lands and bump electrodes may result in acontact defect (conductive defect) originating from insufficient bondingstrength between these lands and bump electrodes.

Moreover, a fluctuation in distance may be caused between lands and bumpelectrodes by a warping of electronic components such as substrates andICs as well as by a fluctuation in the height of lands and bumpelectrodes being formed. This may result in an inability to obtainsufficient bonding strength between the bump electrodes and theterminals, causing a contact defect (conductive defect).

In order to prevent such disadvantages, what has been provided is aprint circuit board that includes a conductive pattern having atrapezoid section, a metal conductive layer formed thereon, and multipleconcavities and convexities applied on a surface of this metalconductive layer (refer to JP-A-2002-261407 for an example).

Such a print circuit board is said to provide improved mounting yield,due to the anchoring effect originating from the concavities andconvexities on the metal conductive surface. The anchoring effectprevents connecting electrodes of a component (electronic component)from slipping or sliding and getting inclined on electrodes on thesubstrate, when pressure is applied during component mounting.

However, while the slipping, the sliding, and the inclination ofconnecting electrodes (bump electrode) arranged over the metalconductive layer are prevented by the anchor effect originating from theconcavities and convexities of the metal conductive surface, theabove-mentioned print circuit board does not have a structure thatincreases the bonding strength between the metal conductive substrateand the connecting electrode. Further, the structure does not increasethe bonding strength between a plurality of electrodes. Consequently,occurrences of the mispositioning during bonding and the misalignmentbetween electrodes (lands and bump electrodes) caused by low aligningprecision therebetween may still result in a contact defect (conductivedefect) originating from insufficient bonding strength between theseelectrodes. Moreover, the connecting electrodes are formed with metal,and therefore exhibit plastic deformation upon coupling. This meansthat, if the distance between the lands and the electrodes are notconstant as described above, the connecting electrodes may have a lowcapability in absorbing the distance deviation with elastic deformation,and therefore the bonding strength between these electrodes may beinsufficient. For this reason, the contact defect (conductive defect)may still occur as well.

SUMMARY

An advantage of the invention is to provide a mounting structure of anelectronic component that exhibits an improved bonding strength betweena bump electrode and a terminal on a substrate with improved reliabilityin a conductive connection status.

According to an aspect of the invention, a mounting structure of anelectronic component includes: a bump electrode included in theelectronic component, the bump electrode having an internal resin as acore and a conductive film covering a surface of the internal resin, andelastically deforming so as to follow a shape of at least one corner ofa terminal so that the conductive film makes direct conductive contactwith at least part of a top surface of the terminal and at least part ofa surface along a thickness direction of the terminal; a substratehaving the terminal and the electronic component that is mounted on thesubstrate; and a holding unit provided to the substrate and theelectronic component so as to hold a state in which the bump electrodeelectrically deformed makes conductive contact with the terminal.

According to this mounting structure of an electronic component, thebump electrode has the internal resin as a core. Therefore, by applyingpressure on the terminal on the substrate, the bump electrode is easilypressed and reaches an elastically (compressively) deformed state.Bonding the bump electrode to the terminal with the aforementionedelastic deformation allows the bump electrode to follow the shape of theterminal, in order for the conductive film to be in directly conductivecontact with at least part of the top surface as well as at least partof the surface along the thickness direction of the terminal, even isthere is, for instance, a misalignment between the bump electrode andthe terminal, causing the bump electrode to abut the corner of theterminal. Therefore, this conductive contact status being held with theholding unit ensures a sufficient contact area between the terminal andthe conductive film of the bump electrode, and this provides apreferable conductive connection status.

Elastic restoring force (repelling force) increases the bonding strengthbetween the internal resin and the terminal, the elastic restoring forcebeing generated in the bump electrode against the terminal of thesubstrate due to the elastic deformation of the internal resin in thebump electrode, thereby improving the reliability of the conductiveconnection status. Specifically, the restoring force of the internalresin caused by the elastic deformation of the bump electrode works sothat the bump electrode wraps the corner, the restoring forceoriginating from following at least one corner shape of the terminal.Therefore, the bonding strength between the bump electrode and theterminal is increased as described.

It is preferable that, in the mounting structure of an electroniccomponent, the holding unit be composed by a sealing resin filled andcured around a conductive contact area of the bump electrode and theterminal.

This ensures the more preferable status of conductive contact betweenthe terminal and the elastically deforming bump electrode, therebyimproving the conductive connection status between the terminal and theconductive film of the bump electrode.

In this case, the bump electrode may be provided to the electroniccomponent in plurality and the terminal is provided to the substrate inplurality. The plurality of terminals may include at least two terminalseach having a different distance from the top surface thereof to asurface of the electronic component for forming the bump electrodes. Thebump electrodes may include at least two bump electrodes correspondingto the at least two terminals, the at least two bump electrodeselastically deforming in a different degree according to the distancefrom each top surface of the at least two terminals to the surface ofthe electronic component for forming the bump electrodes.

In case of the pluralities of the terminals and the bump electrodesrespectively being formed on the substrate and on the electroniccomponent, a substrate distortion may cause a fluctuation in the height(level) of the bonding surface of each of the terminals. This causes thetop surfaces of the plurality of terminals to have different distancesrelative to the forming surface of the bump electrode of the electroniccomponent. Similarly, the electronic component may have an uneven heightat the bonding surface of the bump electrodes.

Moreover, when coupling the substrate and the electronic component atthe pluralities of bump electrodes and terminals, if there is afluctuation in the distance between the bump electrodes and theterminals prior to their bonding, it becomes difficult to couple all thebump electrodes and all the terminals in a preferable strength. Here,the substrate includes terminals with uneven height, and the electroniccomponent includes bump electrodes with uneven height.

However, in the mounting structure according to an aspect of theinvention, the degree of elastic deformation of the bump electrodesvaries in proportion with the distance kept by the top surfaces of theterminals in the electronic component with respect to the formingsurface of the bump electrodes. Therefore, the elastic deformation ofthe bump electrodes absorbs the distance fluctuation between the bumpelectrodes and the terminals. Therefore, a preferable bonding strengthis obtained between the bump electrodes and the terminals, even thoughthe substrate and the electronic component include the terminals and thebump electrodes with an uneven height (level). Consequently, thismounting structure improves the reliability of the conductive connectionstatus at each coupling section, as well as the mounting strength of theelectronic component with respect to the substrate.

It is preferable that, in the mounting structure of an electroniccomponent, the conductive film directly make conductive contact with anentire top surface of the terminal.

Since the conductive film of the bump electrode is in direct conductivecontact with the entire top surface of the terminal, the conductive filmobtains a direct conductive contact with at least part of the surfacealong the thickness direction of the terminal, as well as the entire topsurface of the terminal. Consequently, a large contact area is ensuredbetween the conductive film of the bump electrode and the terminal, andthe preferable conductive connection status is provided. At the sametime, the bonding strength between the bump electrode and the terminalincreases, thereby improving the reliability of the conductiveconnection status.

It is preferable that, in the mounting structure of an electroniccomponent, the surface along the thickness direction include twosurfaces and the conductive film directly make conductive contact withan entire surface of one of the two surfaces.

Since the conductive film of the bump electrode is in direct conductivecontact with one entire surface along the thickness direction of theterminal, the conductive film obtains a direct conductive contact withone entire surface along the thickness direction of the terminal, aswell as at least part of the top surface of the terminal. Consequently,a large contact area is ensured between the conductive film of the bumpelectrode and the terminal, and the preferable conductive connectionstatus is provided. At the same time, the bonding strength between thebump electrode and the terminal increases, thereby improving thereliability of the conductive connection status.

It is preferable that, in the mounting structure of an electroniccomponent, the surface along the thickness direction include twosurfaces and the conductive film directly make conductive contact withat least part of each of the two surfaces.

Further, it is preferable that, in the mounting structure of anelectronic component, the surface along the thickness direction includetwo surfaces and the conductive film directly make conductive contactwith at least part of each of the two surfaces.

Since the conductive film of the bump electrode is in direct conductivecontact with all the surfaces along the thickness direction of theterminal, the conductive film obtains a direct conductive contact withall the surfaces along the thickness direction of the terminal, as wellas at least part of the top surface of the terminal. Consequently, alarge contact area is ensured between the conductive film of the bumpelectrode and the terminal, and the preferable conductive connectionstatus is provided. At the same time, the bonding strength between thebump electrode and the terminal increases, thereby improving thereliability of the conductive connection status.

It is preferable that, in the mounting structure of an electroniccomponent, at least part of one of the internal resin and the conductivefilm abut a surface in a vicinity of the terminal with which theconductive film makes direct contact of the substrate.

Even if there is a fluctuation in the height of the bump electrodes aswell as of the terminals, and even if the fluctuation in the distance istherefore present between the terminals and the bump electrodes prior tothe bonding thereof, after the bonding, the bump electrodes abut thesurface of the substrate in the vicinities of the terminals.Consequently, spots with different compression (elastic deformation)rates are consecutively present inside the internal resin of the bumpelectrodes. Therefore, the bump electrodes include therein the spotswith an optimal coupling force (compression rate) with respect to theterminals, thereby improving the reliability of the bonding (adhesive)property between the bump electrodes and terminals.

Moreover, if the internal resin, in particular, abuts the substratesurface, the internal resin suppresses a current leak (migration)between the adjacent terminals with the internal resin that abuts thesubstrate surface being interposed therebetween.

Further, it is preferable that, in the mounting structure of anelectronic component, at least part of one of the internal resin and theconductive film press and concave a surface in a vicinity of theterminal with which the conductive film makes direct contact of thesubstrate so as to abut the surface.

Since the bump electrode abuts the substrate surface while concaving thesubstrate surface in the vicinity of the terminal, the anchor effectimproves the bonding (adhesive) strength between the bump electrode andthe terminal. Consequently, even if a delaminating force occurs betweenthe bump electrode and the terminal, a preferable conductive connectionstate is ensured against the delaminating force originating from, forinstance, a heat cycle test.

Moreover, as described, there is an improvement in the reliability ofthe bonding (adhesive) property between the bump electrodes and theterminals, and a current leak (migration) is suppressed between theadjacent terminals.

In this case, the internal resin may be formed approximately like abarrel vault with a transverse sectional surface of one of approximatelya half circle, approximately a half oval, and approximately a trapezoid.The conductive film may be provided in a belt-like shape on a topsurface of the internal resin along a direction of the transversesectional surface.

This makes the manufacturing easier, since the plurality of bumpelectrodes is formed by providing, with intervals, the plurality ofconductive films on the top surface of the internal resin.

In this case, the internal resin may be formed either in approximately ahemispheroid or approximately a circular truncated cone, and theconductive film may be provided covering the top surface of the internalresin.

Here, since the bump electrode is curved in all directions from thecenter thereof, in any direction the misalignment may occur relative tothe terminals, the bump electrode follows the corner shape of theterminal in approximately the same state with respect to the terminal.Consequently, it is possible to ensure a stable conductive connectionwith the terminals.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a schematic perspective view illustrating a structure of aliquid crystal device in which an aspect of the invention is applied.

FIGS. 2A and 2B are magnified views of a main part of a mountingstructure according to an aspect of the invention.

FIGS. 3A and 3B are sectional side views illustrating a schematicstructure of a bump electrode.

FIGS. 4A through 4D are drawings for describing the mounting structureaccording to an embodiment.

FIGS. 5A and 5B are magnified plan views for describing structures ofterminals.

FIG. 6 is a drawing for describing the mounting structure according toanother embodiment.

FIG. 7 is a drawing for describing a modification of the mountingstructure according to this embodiment.

FIG. 8 is a drawing for describing the mounting structure according tostill another embodiment.

FIG. 9 is a drawing for describing a modification of the mountingstructure according to this embodiment.

FIG. 10 is a drawing for describing another modification of the mountingstructure according to this embodiment.

FIG. 11 is a perspective view illustrating a schematic structure of thebump electrode.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

An embodiment of a mounting structure according to an aspect of thepresent invention will now be described in detail.

FIG. 1 is a schematic drawing illustrating a liquid crystal device inwhich the mounting structure of an electronic component according to theaspect of the invention is applied. One example application of themounting structure of an electronic component according to the aspect ofthe invention will be described.

A numeral 100 in FIG. 1 indicates a liquid crystal device, and theliquid crystal device 100 is formed including a liquid crystal panel 110and an electronic component (IC chip for liquid crystal drive) 121.Un-illustrated supplementary members such as a polarizing plate, arefection sheet, and backlight are optionally provided to the liquidcrystal device 100 as needed.

The liquid crystal panel 110 is formed including substrates 111 and 112made of glass or synthesized resin. The substrate 111 and the substrate112 are arranged to face each other, and are adhered together by amaterial such as an un-illustrated sealer. Un-illustrated liquidcrystal, which is the electro-optical material, is sealed between thesubstrate 111 and the substrate 112. An electrode 111 a made from atransparent conductive material such as indium tin oxide (ITO) is formedon an inner surface of the substrate 111, and an electrode 112 a isformed on an inner surface of the substrate 112, arranged to face theelectrode 111 a.

The electrode 111 a is coupled with a wiring 111 b formed with the samematerial as an integral unit, and is pulled out onto an inner surface ofa substrate protrusion 111T provided to the substrate 111. The substrateprotrusion 111T is a part that extends outward from an outline of thesubstrate 112 at the edge of the substrate 111. One end of the wiring111 b becomes a terminal 111 bx. The electrode 112 a is coupled with awiring 112 b formed as an integral unit with the same material as thatof the electrode 112 a, and has a conductive connection with a wiring111 c of the substrate 111 through a top-down electrical continuityunit. This wiring 111 c is also formed with ITO. The wiring 111 c ispulled out onto the substrate protrusion 111T, and one end of the wiring111 c becomes a terminal 111 cx. An input wiring 111 d is formed in thevicinity of an end edge of the substrate protrusion 111T, and one end ofthe input wiring 111 d becomes a terminal 111 dx. The terminal 111 dx isarranged to face the terminal 111 bx and the terminal 111 cx. Moreover,the other end of the input wiring 111 d becomes input terminals 111 dy.

The electronic component 121 according to the aspect of the invention ismounted over the substrate protrusion 111T with a sealing resin 122interposed therebetween. The electronic component 121 is, for instance,an IC chip for liquid crystal drive that drives the liquid crystal panel110. Un-illustrated multiple bump electrodes according to the aspect ofthe invention are formed on a lower surface of the electronic component121, and these bump electrodes respectively have a conductive connectionwith the terminals 111 bx, 111 cx, and 111 dx on the substrateprotrusion 111T. This constitutes the mounting structure according tothe aspect of the invention, the mounting structure including theelectronic component 121 mounted on the substrate 111.

A flexible wiring substrate 123 is mounted in an array area of the inputterminals 111 dy on the substrate protrusion 111T with an anisotropicconductive film 124 imposed between the array area and the flexiblewiring substrate 123. The input terminals 111 dy respectively have aconductive connection with un-illustrated corresponding wirings that areprovided to the flexible wiring substrate 123. The input terminals 111dy are supplied with control signals, imaging signals, and powerpotentials from an external source through this flexible wiringsubstrate 123. The control signals, imaging signals, and powerpotentials supplied to the input terminals 111 dy are input into theelectronic component 121 in which the drive signals for driving liquidcrystal are generated so as to be supplied to the liquid crystal panel110. It is common and preferable that the flexible substrate be aflexible organic substrate formed with materials such as polyimide andliquid crystal polymer, and that circuit patterns and terminals beformed on that substrate with copper and aluminum. However, theconfiguration of the flexible substrate is not limited thereto. It ismore preferable that the terminals be gold plated, so as to stabilizethe connection resistance.

The liquid crystal device 100 with the above structure allowsmodification of light independently for each pixel which is formed inthe area in which the electrodes 111 a and 112 a are counter arranged,by impressing appropriate voltages between the electrode 111 a and theelectrode 112 a through the electronic component 121, thereby forming adesired image in a display area of the liquid crystal device 100.

Embodiments of the mounting structure of the electronic componentapplied to the liquid crystal device 100 according to the aspect of theinvention will now be described.

FIG. 2A is a magnified perspective view illustrating a main part of themounting structure of the electronic component 121 of the liquid crystaldevice 100. FIG. 2B is a sectional view along A-A line in FIG. 2A. Anumeral 11P in FIGS. 2A and 2B indicates a wiring pattern provided onthe substrate 111, and a numeral 11 indicates the terminals installed inthe wirings, i.e. any of the above-described terminals 111 bx, 111 cx,and 111 dx. In this embodiment, the terminals 11 have a relatively thickfilm thickness, which therefore means that the height of the terminals11 is tall, and the cross section thereof is approximately trapezoid. Anumeral 12 each indicates a bump electrode provided to the electroniccomponent 121. The sealing resin 122 is, as illustrated in FIG. 2B,while the illustration thereof is omitted in FIG. 2A, disposed to befilled and cured between the substrate 111 and the electronic component121, the sealing resin 122 covering around at least a conductive contactarea of the bump electrodes 12 and of the terminals 11. It is preferablethat the sealing resin 122 be resins such as epoxy, acrylic, and phenol,while the type of resin is not limited thereto, as long as the materialbeing used is resin.

In these embodiments, as illustrated in FIG. 2A, FIGS. 3A and 3B, eachof the bump electrodes 12 has, as a core, a structure which includesinternal resin 13 shaped approximately like a barrel vault provided onthe electronic component 121, with a surface of the internal resin 13being covered by a conductive film 14. The conductive film 14 is, asshown in FIGS. 3A and 3B, disposed on the surface of the electroniccomponent 121, so as to be coupled and electrically continued to anelectrode 16 exposed to an opening in an insulating film 15, and is leadonto the internal resin 13. The conductive film 14 covering the surfaceof the internal resin 13 in such a structure is electrically continuedto the electrode 16, thereby substantially functioning as an electrodeof the electronic component 121. In these embodiments, the conductivefilm 14 is provided in plurality, and conductive films 14 each shapedlike a band are provided on the surface of the internal resin 13. Eachof these conductive films 14 is independently coupled and electricallycontinued to the electrode 16 of the electronic component 121.Therefore, these conductive films 14 independently function, togetherwith the internal resin 13 positioned at an inner side of eachconductive film 14, as the bump electrodes 12 according to the aspect ofthe invention.

Here, the aforementioned “approximately a barrel vault shape” means acolumnar shape in which the inner (bottom) surface that is in contactwith the electronic component 121 is flat, and the outer surface that isnot in contact therewith is curved. Specifically, the preferably usedbump electrodes 12 have sectional shapes such as approximately halfcircle as shown in FIG. 3A, approximately half oval (not illustrated),and approximately trapezoid as shown in FIG. 3B. Here, each of the bumpelectrodes 12 with the approximately trapezoid cross-sectional shape asshown in FIG. 3B has a bent at least at a shoulder between the top andthe side in this cross-sectional shape. This makes, as described, theouter surface that is not contact with the electronic component 121 acurved surface.

The internal resin 13 is formed with photosensitive resin andthermosetting resin, specifically, resins such as polyimide, acrylic,phenol, silicone, silicone-modified polyimide, and epoxy resins. Suchinternal resin 13 is formed, as described, approximately like a barrelvault by known techniques of lithography and etching. The material ofresin (hardness) and its detailed shape of the approximate barrel vault(heights and widths) are optionally selected and designed in accordancewith the shape and the size of the terminals 11 as described below.

The conductive films 14 are made of metals and alloys such as Au, TiW,Cu, Cr, Ni, Ti, W, NiV, Al, Pd, and lead-free solder, and may be any oneof a single layer and a multilayer of these metals (alloys). Suchconductive films 14 may be deposited with a known film deposition methodsuch as sputtering and thereafter be patterned into a band shape, or,may be selectively formed by electroless plating. Alternatively, anunderlying film may be formed with methods such as sputtering andelectroless plating, and thereafter an upper layer film may be formedthereon with electroplating, so as to form the conductive films 14 witha multilayer film composed with the underlying film and the upper layerfilm. The type, a layer structure, a film thickness, and width of themetal (alloy) are optionally selected and designed, similar to the caseof internal resin 13, in accordance with the shape and the size of theterminals 11. However, it is preferable that gold (Au) that excels, inparticular, in flatting property be used for the conductive films 14,since the conductive films 14 elastically deform following corner shapesof the terminals 11 as will be described later. Moreover, in case offorming the conductive films 14 in multilayer, it is preferable thatgold be used on the outermost layer. Moreover, it is preferable that thewidth of the conductive films 14 be sufficiently wider than that of theterminals 11 to be bonded.

FIG. 4A is a drawing illustrating a status before mounting theelectronic component 121 to the substrate 111, and is a magnifiedsectional view corresponding to the main parts of the FIG. 2B.Hereafter, the terminals 11, the bump electrodes 12, and the conductivefilms 14 are described in singular. The substrate 111 and the electroniccomponent 121 are positioned so that the terminal 11 and the bumpelectrode 12 face each other. In this state, a pressure is applied tothe direction to bond each other, so that the conductive film 14 of thebump electrode 12 is bonded with the terminal 11 as shown in FIGS. 4Band 4C, thereby having a conductive contact. In the state of theconductive film 14 and the terminal 11 having a conductive contact, inother words, in a state in which a predetermined pressure is applied,the sealing resin 122 (refer to FIG. 2B) as the holding unit accordingto the aspect of the invention is filled and cured between the substrate111 and the electronic component 121. Consequently, a mounting structure10 as a first embodiment of the invention is obtained. At this time, thesealing resin 122 as the holding unit may be provided in advance betweenthe substrate 111 and the electronic component 121 in a non-cured state(or half cured state), so as to be cured after making the a conductivecontact between the conductive film 14 and the terminal 11. Moreover,the filling of the sealing resin 122 between the substrate 111 and theelectronic component 121 may be carried out after making a conductivecontact between the conductive film 14 and the terminal 11, and may becured thereafter.

In the mounting structure 10 formed as described and is recited as thefirst embodiment of the invention, the electronic component 121 ispressed relative to the substrate 111, and the bump electrode 12 abutsthe terminal 11 and is further pressed in this status, so as to beelastically (compressively) deformed into desired shapes. In otherwords, the bump electrode 12 that includes internal resin 13 as a coreis sufficiently flexible compared to the terminal 11 which is made ofmetal, and therefore is elastically deformed and compressed by theapplied pressure. At this time, since the internal resin 13 and theconductive film 14 thereon are formed to be wider than the terminal 11,they bulge around the terminals 11 (to the side surface thereof), andtake shapes that follow all the corner shapes of the terminals 11.

In other words, the bump electrode 12 follows the shapes of all thecorners of the terminal 11 by elastic deformation mainly of the internalresin, thereby providing the conductive film 14 with a direct conductivecontact with at least part of a top surface of the terminal 11 as wellas all the surfaces along a thickness direction of the terminal 11.Here, referring to FIG. 4D which is a magnified view of FIG. 4B, sidesurfaces 11 b positioned at both sides of a top surface 11 a of theterminal 11 indicate the surfaces along the thickness direction, and thecorners are indicated by corners 11 c which are formed by the topsurface 11 a meeting the side surfaces 11 b. In this embodiment, thecross-sectional shape of the terminal 11 is approximately trapezoid.However, it may also be rectangular. Moreover, the terminal 11 may alsobe relatively thin (short), and not limited to being thick (tall), interms of the thickness (height) thereof.

The terminal 11 of the substrate 111 may be, as illustrated in amagnified plan view of FIG. 5A, an end point of a wiring pattern 11P. Inthis case, as shown in oblique lines in FIG. 5A, a region which has apreset length when measured from the end edge of the wiring pattern 11Pbecomes the terminal 11 according to the aspect of the invention. Theterminal 11 may also be, as illustrated in a magnified plan view of FIG.5B, a region indicated in oblique lines, i.e. a land formed to be widerthan the wiring pattern 11P at its end. In the mounting structure 10shown in FIG. 4D, the conductive film 14 of the bump electrode 12 is indirect conductive contact with the top surface of the terminal 11, i.e.the entire surface of the region (the whole region) illustrated in FIGS.5A and 5B.

The bump electrode 12 follows the shapes of all the corners of theterminal 11 by elastic deformation, and therefore the conductive film 14is, as described, also in a direct conductive contact with a part of theside surfaces 11 b of the terminal 11. In the case of the terminal 11having a shape shown in FIG. 5A, the conductive film 14 is also indirect conductive contact with a part of an outer surface 11 d of theterminal 11, the outer surface 11 d being an end edge of the wiringpattern 11P. In the case of the terminal 11 having a shape shown in FIG.5B, in addition to the outer surface 11 d of the terminal 11, theconductive films 14 are also respectively in direct conductive contactwith a part of an inner surface 11 e at the opposite side of the outersurface 11 d.

Here, while in FIG. 4D, the conductive film 14 contacts approximately anupper half of the side surfaces 11 b, it may also contact only the topends of the side surfaces 11 b. In addition, the conductive film 14 maycontact only the top ends of the outer surface 11 d and inner surface 11e. In other words, in the mounting structure according to the aspect ofthe invention, the conductive film 14 needs to contact, by following thecorner shapes of the terminals 11, only a part of the side surfaces 11b, the outer surface 11 d, and the inner surface 11 e. That is to say,the bump electrode 12 following the corner shapes of the terminal 11 byelastic deformation allows the conductive film 14 to contact at least apart of the side surfaces 11 b, the outer surface 11 d, and the innersurface 11 e of the terminal 11.

In this mounting structure 10, the bump electrode 12 following thecorner shapes of the terminal 11 allows the conductive film 14 to be indirect conductive contact with the entire top surface 11 a, as well as apart of the side surfaces 11 b, the outer surface 11 d, and the innersurface 11 e of the terminal 11. Moreover, this state of conductivecontact is held by the sealing resin 122. Therefore, sufficient amountof contact areas are ensured between the conductive film 14 and theterminal 11, providing a favorable conductive connection therebetween.Elastic restoring force (repelling force) generated against the terminal11 due to the elastic deformation of the internal resin 13 of the bumpelectrode 12 increases the bonding strength between the bump electrode12 and the terminal 11, thereby improving the reliability of theconductive connection status. Specifically, the bump electrode 12follows the shapes of the corners 11 c of the terminal 11 with theelastic deformation, so that the restoring force of the internal resin13 works in a away that the corners 11 c are wrapped. Therefore, thebonding strength between the bump electrode 12 and the terminal 11 isincreased as described. Consequently, the mounting structure 10according to the first embodiment has an excellent property of improvedreliability in the conductive connection status with sufficientlyimproved bonding strength between the bump electrode 12 and the terminal11.

FIG. 6 is a drawing illustrating a second embodiment of the mountingstructure of the electronic component according to the aspect of theinvention. The second embodiment is different from the first embodimentshown in FIG. 4D in that the conductive film 14 in the bump electrode 12follows only the corners 11 c of one side, and not the corners 11 c ofboth sides.

In recent years, size reduction, as well as an increase in the degree ofhigh-integration of mounting structures of electronic components areaccelerating, and so as the narrowing of wiring pitch and a wiringwidth. Therefore, due to the misalignment of bump electrodes andterminals and the mispositioning of substrates and electronic componentsduring the manufacturing, sufficient bonding strength cannot be obtainedbetween these bump electrodes and the terminals, and this may cause acontact defect (conductive defect).

For this reason, the mounting structure in the second embodiment has astructure that prevents the contact defect even there is a misalignmentor a misposition.

Specifically, in a mounting structure 20 shown in FIG. 6, themisalignment and the misposition cause the bump electrode 12 to jolt outof alignment in the width direction of the terminal 11, i.e. the wiringpattern 11P referred in FIGS. 5A and 5B. Therefore, the conductive film14 is not in direct contact with an entire surface of the top surface 11a of the terminal 11, and is in direct contact with only one of the sidesurfaces 11 b. Even with the misalignment in the mounting structure 20in this embodiment however, the shape of the corners 11 c at one side ofthe terminal 11 is followed, as described. Therefore the conductive film14 is in direct conductive contact with a part of the top surface 11 aas well as a part of at least one of the side surfaces 11 b of theterminal 11. Moreover, this state of conductive contact is held by theun-illustrated sealing resin 122.

Therefore, sufficient amount of contact areas are ensured between theconductive film 14 and the terminal 11, providing a favorable conductiveconnection therebetween. Elastic restoring force (repelling force)generated against the terminal 11 due to the elastic deformation of theinternal resin 13 of the bump electrode 12 increases the bondingstrength between the bump electrode 12 and the terminal 11, therebyimproving the reliability of the conductive connection status. Since therestoring force of the internal resin 13 works so as to wrap one of thecorners 11 c, the bonding strength between the bump electrode 12 and theterminal 11 increases as described above.

Consequently, the mounting structure 20 formed including themisalignment and the misposition inherent therein also prevents contactdefects and has an excellent property of improved reliability in theconductive connection status, with sufficiently improved bondingstrength between the bump electrodes 12 and the terminals 11.

The characteristics of the internal resin 13, particularly the hardnessand the elastic deformability (compressive property), may be optionallymodified in accordance with attributes such as the type and compositionof the resin as well as a processing condition. The degree of elasticdeformation of the bump electrode 12 during the mounting may also bemodified in accordance with attributes such as a pressure conditionbetween the substrate 111 and the electronic component 121. Based on theabove, as a modification of the second embodiment, it may be that thedegree of the elastic deformation (compression) of, in particular, thebump electrode 12 is increased, so that the conductive film 14 abut theentire surface of one of the side surfaces 11 b as shown in FIG. 7.

This ensures a large contact area between the conductive film 14 and thebump electrode 12 of the terminal 11, thereby providing a preferablestate of conductive connection. Moreover, the bonding strength betweenthe bump electrode 12 and the terminal 11 is increased and thereliability in the state of conductive connection is improved.

FIG. 8 is a drawing illustrating a third embodiment of the mountingstructure of the electronic component according to the aspect of theinvention. The third embodiment is different from the first embodimentshown in FIG. 4D in that there are the pluralities of bump electrodes 12and terminals 11 respectively provided on the electronic component 121as well as on the substrate 111, so that the bonding (coupling) isconducted between the pluralities of bump electrodes 12 and terminals11, and that, in particular, the height levels of the terminals 11 areuneven.

In the case where the plurality of the terminals 11 is formed on thesubstrate 111, a distortion of the substrate 111 and the like may causea fluctuation in the height (level) of the bonding surface (top surface)of each of the terminals 11 relative to the bump electrodes 12. Thismeans that the top surfaces (bonding surfaces) of these terminals 11have different distances relative to the forming surface of the bumpelectrodes 12 of the electronic component 121. Similarly, the electroniccomponent 121 may have an uneven height at the bonding surface of thebump electrodes 12.

As described, when coupling the substrate 111 to the electroniccomponent 121 at the pluralities of bump electrodes 12 and the terminals11, while there is a fluctuation in the distance between these bumpelectrodes 12 and the terminals 11 prior to their bonding, thisfluctuation makes it difficult to couple all the bump electrodes 12 withall the terminals 11 in a preferable strength. Here, the substrate 111includes the terminals 11 with uneven height, and the electroniccomponent 121 includes the bump electrodes 12 with uneven height.

However, a mounting structure 30 according to the third embodiment shownin FIG. 8 has a preferable bonding (coupling) state between a terminal11A and one of the bump electrodes 12 as well as between a terminal 11Band another one of bump electrodes 12, even when the substrate 111distortion causes the height of the terminal 11A to be different fromthat of the terminal 11B. In other words, even when a distance L1 isdifferent from a distance L2, the distance L1 being a distance betweenthe top surface 11 a of the terminal 11A and the forming surface of thebump electrodes 12 of the electronic component 121, and the distance L2being the distance between the top surface 11 a of the terminal 11B andthe forming surface of another one of the bump electrodes 12.

That is to say, in this mounting structure 30, the elastic deformationof the bump electrodes 12 absorbs a difference between the distance L1and the distance L2, i.e. the fluctuation in the distance between thebump electrodes 12 and the terminals 11. Here, the degree of elasticdeformation changes inside the bump electrodes 12, each of whichcontaining the internal resin 13, in proportion with the distance L1 andthe distance L2 relative to the terminals 11 to be bonded. Consequently,the substrate 111 and the electronic component 121 obtain a preferablebonding strength between the bump electrodes 12 and the terminals 11,since the elastic deformation of the bump electrodes 12 absorbs thefluctuations in the height (level) of the terminals 11 as well as of thebump electrodes 12.

It is preferable that the degree of elastic deformation (compression) ofthe bump electrodes 12 be increased, if the pluralities of terminals 11and the bump electrodes 12 are bonded (coupled). In other words, it ispreferable that each of the bump electrodes 12 partly abuts the surfaceof the substrate 111 in a vicinity of each of the terminals 11 so as tohave a conductive contact with the terminals 11, as illustrated as amounting structure 40 shown in FIG. 9. Here, the degree of elasticdeformation may be increased by increasing deformability (compressiveproperty) of the internal resin 13, and/or by increasing the pressureforce between the substrate 111 and the electronic component 121 duringthe mounting. The bump electrodes 12 referred to above include not onlythe conductive films 14 and the internal resin 13 covered by theconductive films 14, but also the internal resin 13 present in thevicinities of the conductive films 14, i.e. the internal resin 13 beingexposed and not covered by the conductive films 14.

Even if the fluctuation in the distance between the terminals 11 and thebump electrodes 12 is present prior to the bonding thereof, after thebonding, the bump electrodes 12 abut the surface of the substrate 111 inthe vicinities of the terminals 11. Consequently, the elasticdeformation of the bump electrodes 12 ensures the absorption of theaforementioned fluctuation in the height of the terminals 11 and of thebump electrodes 12. Therefore, in this mounting structure 40, apreferable bonding strength is obtained between the bump electrodes 12and the terminals 11. Moreover, spots with different compression rate(elastic deformation rate) are consecutively present inside the internalresin 13 of the bump electrodes 12. Therefore, the bump electrodes 12include therein the spots with an optimal coupling force (compressionrate) relative to the terminals 11. This improves the reliability of thebonding (adhesively) between the bump electrodes 12 and the terminals11.

Moreover, since the internal resin 13 positioned in the vicinities ofthe conductive films 14 abut the surface of the substrate 111, theinsulating internal resin 13 prevents a current leak (migration) betweenthe adjacent terminals 11A and 11B with the internal resin 13 abuttingthe surface of the substrate 111 interposed therebetween.

In the case of bonding (coupling) the pluralities of terminals 11 andbump electrodes 12, it is preferable that a part of the respective bumpelectrodes 12 abut the surface of the substrate 111 in a state in whichthe bump electrodes 12 press the surface of the substrate 111 in thevicinities of the terminals 11, concaving the surface of the substrate111, so that the bump electrodes 12 conductively contact the terminals11, as in a mounting structure 50 shown in FIG. 10. This is achieved byadjusting the deformability (compressive property) of the internal resin13 as well as the pressure force between the substrate 111 and theelectronic component 121 during the mounting.

Even if the fluctuation in the height of the terminals 11 and of thebump electrodes 12 is present, the bump electrodes 12 abut and press thesurface of the substrate 111 in the vicinities of the terminals 11.Consequently, the elastic deformation of the bump electrodes 12 ensuresthe absorption of the aforementioned fluctuation. Therefore, in thismounting structure 50, a preferable bonding strength is obtained betweenthe bump electrodes 12 and the terminals 11.

Moreover, the bump electrodes 12 abut the surface of the substrate 111in the vicinities of the terminals 11 while concaving the substrate 111.This further increases the bonding (adhesive) strength of the bumpelectrodes 12 relative to the terminals 11 by the anchoring effect.Consequently, even if a delaminating force occurs between the bumpelectrodes 12 and the terminals 11, a preferable conductive connectionstate is ensured against this force. Here, the delaminating forceoriginates from, for instance, a heat cycle test.

Moreover, since the internal resin 13 positioned in the vicinities ofthe conductive films 14 abuts the surface of the substrate 111, theinsulating internal resin 13 prevents a current leak (migration) betweenthe adjacent terminals 11A and 11B with the internal resin 13 abuttingthe surface of the substrate 111 interposed therebetween.

The present invention shall not be limited to the above-mentionedembodiments, and may allow various modifications without departing fromthe main scope of the present invention. For example, as for thestructure of the bump electrode, the internal resin is not limited to beshaped approximately like a barrel vault as shown in FIG. 2A as well asin FIGS. 3A and 3B. As shown in FIG. 11, an internal resin 17 may beformed approximately in hemispheroid, and a conductive film 18 may coveran entire top surface of the internal resin 17, the conductive film 18being provided in a state electrically continuing to the electrode 16 ofthe electronic component.

Employing such a structure allows this bump electrode to follow thecorner shapes of each of the terminals 11 in approximately the samestate with respect to the terminals 11, even if the misalignment occursin any direction relative to each of the terminals 11, since this bumpelectrode is curved in every direction with approximately the samecurvature from the center of the internal resin 17. Consequently, it ispossible to ensure a stable conductive connection with each of theterminals 11. The shape of the internal resin 17 may also be a circulartruncated cone, in addition to an approximate hemispheroid. Moreover,the conductive film 18 may be provided to cover only a part of the topsurface of the internal resin 17 shaped approximately in a hemispheroidor in a circular truncated cone, without covering its entire topsurface.

Moreover, in the embodiments described above, the sealing resin 122 isused as the holding unit according to the aspect of the invention, whilevarious mechanical compressing means such as binding by screwing,clipping, and fitting may also be employed. In case of using adhesives(resin), the adhesive may also be selectively disposed, for instance,only between the periphery of the electronic component and thesubstrate, without being filled around the conductive contact area ofthe bump electrodes 12 as well as of the terminals 11.

Moreover, instead of the substrate made of glass and synthesized resin,various kinds of substrates may be used for the substrate 111 such asrigid substrate, silicon substrate, and thin ceramics substrate.Examples of electronic component includes, in addition to an IC chip forliquid crystal drive, any electronic component that has a connectingelectrode (bump electrode) described above, including various integratedcircuits and passive components such as diodes, transistors,light-emitting diode, laser diode, oscillator, and capacitors.

Examples of devices in which the mounting structure of the electroniccomponent according to the aspect of the invention is applied include,in addition to the liquid crystal display device described above, anorganic electroluminescence device (organic EL device), a plasma displaydevice, an electrophoretic display device, and devices utilizingelectroemissive elements (such as field emission display andsurface-conduction electron-emitter display). These devices may beapplied to various electro-optical devices and electronic modules.

What is claimed is:
 1. An electronic device comprising: a substratehaving a terminal; an electronic component including a bump electrode,the bump electrode comprising: a conductive film having contact with theterminal; and a resin covered by the conductive film; and an adhesivehaving contact with the substrate and the electronic component, whereinthe conductive film contacts with at least part of a top surface of theterminal and at least part of a lateral surface of the terminal.
 2. Theelectronic device according to claim 1, wherein the adhesive is composedof a sealing resin filled and cured around a conductive contact area ofthe bump electrode and the terminal.
 3. The electronic device accordingto claim 1, wherein: the bump electrode is provided to the electroniccomponent in plurality and the terminal is provided to the substrate inplurality; the plurality of terminals includes at least two terminalseach having a different distance from the top surface thereof to asurface of the electronic component for forming the bump electrodes; andthe bump electrodes include at least two bump electrodes correspondingto the at least two terminals, the at least two bump electrodeselastically deforming to a different degree according to the distancefrom each top surface of the at least two terminals to the surface ofthe electronic component for forming the bump electrodes.
 4. Theelectronic device according to claim 1, wherein the conductive filmdirectly makes conductive contact with an entire top surface of theterminal.
 5. The electronic device according to claim 1, wherein thelateral surface includes two surfaces and the conductive film directlymakes conductive contact with an entire surface of one of the twosurfaces.
 6. The electronic device according to claim 1, wherein thelateral surface includes two surfaces and the conductive film directlymakes conductive contact with at least part of each of the two surfaces.7. The electronic device according to claim 1, wherein at least part ofone of the resin and the conductive film abuts a surface of thesubstrate in a vicinity of the terminal with which the conductive filmmakes direct contact.
 8. The electronic device according to claim 7,wherein at least part of one of the resin and the conductive filmconcavely depresses a surface of the substrate in a vicinity of theterminal with which the conductive film makes direct contact so as toabut the surface of the substrate.
 9. The electronic device according toclaim 1, wherein: the resin is formed approximately like a barrel vaultwith a transverse sectional surface of one of approximately a halfcircle, approximately a half oval, and approximately a trapezoid; andthe conductive film is provided in a belt-like shape on the surface ofthe resin along a direction of the transverse sectional surface.
 10. Theelectronic device according to claim 1, wherein: the resin is formed inone of approximately a hemispheroid and approximately a circulartruncated cone; and the conductive film is provided covering the surfaceof the resin.